Safety blasting cap



ug. 24, 1943- .1. G. .JOHNSON 2,327,902

SAFETY BLASTING CAP Filed NOV. 14, 1940 HU @mao/a Horn@ HUH I ,UUR

UNITED STATES PATENT OFFICE SAFETY BLASTING CAP John G. Johnson, LeadCity, S. Dak.

Application November 14, 1940, Serial No. 365,701

2 Claims.

The present invention relates to new and useful improvements in blastingcaps for use in all kinds of blasting operations, including coal mining,wherein dynamite or highly explosive powder is used, and has for itsprimary object to provide, in a manner as hereinafter set forth, adevice of this character which, in the event of a misiire, will becomeharmless after a predetermined length of time, thereby promoting safety.

Another very important object oi the invention is to provide a blastingcap of the aforementioned character which is adapted to be bent atspaced points at relatively sharp or acute angles without breaking.

Other objects of the invention are to provide a blasting cap of thecharacter described which will be comparatively simple in construction.highly eiilcient and reliable in use, light in weight and which may bemanufactured at low cost.

All of the foregoing and still further objects and advantages oi theinvention will become apparent from a study oi' the followingspecilication, taken in connection with the accompany,- ing drawingwherein like characters of reference designate corresponding partsthroughout the several views, and wherein:

Figure 1 is a view in side elevation oi a safety blasting capconstructed in accordance with the present invention, showing said capin position in a charge which has been placed upside down in a hole.

Figure 2 is a view in vertical longitudinal section through the cap.

Figure 3 is a perspective view of the cap.

Referring now to the drawing in detail, it

will be seen that the embodiment of the invention which has beenillustrated comprises a tubular casing I which is formed oi' rolledpaper. The paper of which the rolled tubular casing I is made is oi atexture to absorb and permit the passage of moisture or water in apredetermined length of time. One end of the tubular casing I is closed,as at 2.

The closed end portion of the tubular casing I is internally reduced forproviding an explosive chamber 3. The explosive chamber 3 is formed fromsuitable light cardboard or paper rolled into a tube 4. Thus, a shoulderor abutment 5 is provided in this end portion oi the tubular casing I.

The tubular casing I is of Just suilicient diameter to nicely receivethe usual fuse 8. However, the fuse 8 is too large to enter theexplosive 4 chamber 3 but engages or abuts the shoulder i. Split clamps1 are bent around the tubular casing I at longitudinally spaced pointsfor contracting said casing and frictionally securingv same on the fuse6. The clamps 1 also positively prevent the tubular casing I fromunrolling.

In Figure 1 of the drawing, the reference numeral 8 designates a chargein a, hole 9. When using the cap constituting the present inven.

tion, the fuse 6 is inserted in the tubular casing and the charge isreadyI to be red. Should a misiire occur, moisture or water will, withina predetermined time, penetrate the tubular cas- 'ing I and theexplosive chamber 4 and render the powder or dynamite in said chamber 4harmless. It isv believed that the many advantages of a blasting capconstructed in accordance with the present invention will be readilyunderstood and although a preferred embodiment of the device is asillustrated and described, it is to be understood that changes in thedetails of construction may be resorted to which will fall within thescope of the invention as claimed.

What is claimed is: 1. A blasting cap comprising-a rolled tube ofabsorbent paper capable of constituting a exible casing of uniformdiameter for the reception of a fuse in one end. said casing includingan internally reduced, closed end portion consti- 'tuting a chamber atthe other end of the tube,

an explosive in said chamber, and clamps detachably securedto the-casing for contracting the casing and frictionally securing same on afuse.

2. A blasting cap oi the character described comprising a tubular casingof uniform diameter, said casing being constructed of bendable,absorbent material ior the reception of a fuse in one end of the casing.a tubular explosive chamber in the other end portion oi.' the casing.an-

